That link contained this:
"The power rating of a PC power supply is not officially certified and is self-claimed by each manufacturer.[1]A common way to reach the power figure for PC PSUs is by adding the power available on each rail, which will not give a true power figure. This means that you cannot use the PSU maximum rating on one rail, but only as a total. Therefore you can overload a PSU on one rail without having to use the maximum rated power."

Also further down:
"The ATX12V 2.x and EPS12V power supply standards defer to the IEC 60950 standard, which requires that no more than 240 volt-amps be present between any two accessible points. Thus, each wire must be current-limited to no more than 20 A"

Ohms law: 240 watt power supply MAX, with about 120mv ripple.

I just replaced a Thermaltake PS, It is rated at 600 watts total, with several +12V sections (18A) = 226 watts.

you need to find out first how many amps your amplifier is pulling.if your amp has 2-25 amp fuses that is 50amps,always add the fuses in the amp together.your pwr supply is 60amps consider running a fuse on the power wire from the supply to the amp,keep in mind the the amplifiers fuses needed to be added together. for 400watt amp non- class d amp 2-channel i would use a 60amp fuse and that should do it!! any questions feel free to give me a call@TTH Electronics-330-430-0041 jerome